NEW TECHNOLOGIES
IN SOLID WASTE
i
MANAGEMENT
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Single copies of this publication
are available from solid waste
management publications distri-
bution unit, U.S. Environmental
Protection Agency, Cincinnati,
Ohio 45268.
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NEW TECHNOLOGIES IN
SOLID WASTE MANAGEMENT
by Clyde J. Dial*
Exhaustion of the Nation's
resource base is a very real possi-
bility. Currently, a few industries
recycle waste materials, recpgnizing
the long-term economic advantages
of recovered waste materials over
raw or primary materials. But this
recognition has not significantly
reversed the trend toward greater
waste generation nor has it reduced
the burden on communities across
the Nation that are responsible for
the.day-to-day management of solid
waste materials.
As President Nixon pointed out
in his 1970 message to Congress on
*Director, Systems Management
Division, Office of Solid Waste
Management Programs, U.S. Environ-
mental Protection Agency.
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the environment, "If we are ever
truly going to gain control of the
problem, our goal must be broader:
to reduce the volume of wastes and
the difficulty of their disposal,
and to encourage their constructive
reuse instead. . . ,
"As we look toward the long-
range future—1980, 2000, and
beyond--recyc1ing of materials will
become increasingly necessary not
only for waste disposal but also to
conserve resources. While our
population grows, each one of us
keeps using more of the earth's
resources. In the case of many
common minerals, more than half of
those extracted from the earth since
time began have been extracted since
1910."
The first concentrated effort
by,the Federal government to miti-
gate the Nation's solid waste
problems began with passage of
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the Solid Waste Disposal Act
(P.L. 89-272) in October 1965. The
Act had two major purposes:
1. To initiate and accelerate
a national research and develop-
ment program for new and improved
methods of proper and economic
solid waste disposal;
2. To provide technical and
financial assistance to State and
local governments in the planning,
developing, and conducting of
solid waste disposal programs.
Since the Act was passed,
Congress authorized $79,950,000
and appropriated $6^,763,000
through fiscal year 1970. Of the
appropriated amount, $60,27^,000
was actually spent. The budget
for fiscal 1971 is $20,500,000.
During this time, the Office of
Solid Waste Management Programs
placed increasing emphasis on de-
veloping methods for recycling
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solid waste materials while it
continued to investigate new collec-
tion, processing, and disposal
techni ques.
MATERIAL RECYCLING
Mixed Solid Wastes. Success
in reusing large amounts of solid
wastes depends on finding some
economical way to separate the com-
ponents. As an example of projects
in this area, the Stanford Research
Institute was engaged to determine
the technical feasibility of using
an air classification process to
separate nonhomogeneous, dry, solid
waste materials. A pilot air
classifier, constructed to separate
five such materials, operates on
the principle that a sufficient
velocity of air passing upward
thro.ugh the mixed wastes will
separate them by particle size,
configuration, and specific gravity.
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This research project received
additional support from the Glass
Container Manufacturers Institute,
Inc., after the contract for the
project was completed. Through a
grant to the Franklin Institute,
the OSWMP is currently evaluating
a device to separate municipal
trash into its various components.
The solid waste separator works
basically on mechanical principles;
it consists of a series of vi-
brating screens, baffler, a paddle
wheel, and a gravity separator.
The OSWMP is also supporting
the evaluation of a pilot-scale
separator at Vanderbilt University.
The unit employs a high-energy,
high-strength magnetic field to
separate shredded nonmagnetic
metals, based on the difference
in the electromagnetic properties
of the waste components.
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A pilot-scale wet pulveriza-
tion system, designed to reclaim
fiber from municipal solid waste,
has been developed and successfully
demonstrated. The incoming solid
waste is dumped into a storage
hopper from which it is fed con-
tinuously into a Hydrapulper and
then forced through 1/2-inch holes.
Heavy inorganic materials are
removed by a bucket elevator. The
pulped material passes through a
liquid cyclone to separate such
heavy materials as dirt, glass, and
small bits of metal. The remaining
organic material passes through a
series of screens that progressively
concentrate the paper fiber. It is
estimated that 1,000 tons of solid
waste might yield 200 tons of paper
fiber, 80 tons of ferrous metals.
and 80 tons of glass cullet.
Specific Solid Wastes. At
Louisiana State University, a pilot
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plant is successfully turning
cellulose (bagasse) into a single-
cell protein substance. The
facility was built after University
scientists discovered a micro-
organism that breaks down waste
cellulose into protein. Additional
work is being conducted to refine
processing techniques and to
analyze the protein products for
digestibility and nutritional
va1ue.
It has been demonstrated on
a pilot scale that waste glass can
be used as an aggregate in bitumi-
nous mixtures to maintain and pave
streets. Glasphalt, the name
given this mixture, may help solve
urban glass waste disposal problems.
SOLID WASTES AS ENERGY SOURCES
Three systems are under in-
vestigation that can process mixed
municipal solid wastes and convert
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them into energy, a diminishing
resource in the United States at
this time. Solid waste has a heat-
ing value about half that of coal
and a sulfur content about one-
tenth that of presently utilized
coal.
Supplementary Fuel. A project
underway in St. Louis indicates that
it is feasible to use ground munici-
pal solid waste as a supplementary
fuel for a coal-fired power plant.
A full-scale demonstration unit is
being built with the cooperation of
a private utility and is scheduled
to begin operating in early 1972.
Ten to 20 percent of the total
furnace charge, by weight, will be
solid waste; larger amounts would
cause ash-handling and air pollution
p rob 1 ems.
• Generation of Electricity. An
advanced engineering concept in
the solid waste management field
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is that involving the CPU-AOO,
which is being developed under
contract by the Combustion Power
Company of Palo Alto, California.
As presently configured, the
CPU-400 is a fluidized-bed incin-
erator that burns solid wastes at
high pressure. The hot gases that
are produced power a turbine that
drives an electrical generator.
The designers of the CPU-JtOO esti-
mate that it should be able to
produce approximately 15,000 kilo-
watts while processing 400 tons of
municipal solid wastes daily. This
would represent 5 to 10 percent of
the power requirements of the
community providing the solid
waste and partially offset the
cost of waste disposal. In addi-
tion, solid waste haul distances
could be greatly reduced by having
units at strategic points in urban
areas. A one-tenth-scale pilot
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plant is scheduled for completion
in mid-1972, and a full-size proto-
type after 197^.
Production of S team. In Lynn,
Massachusetts, the OSWMP has sup-
ported the successful evaluation
of the feasibility of using a
spreader-stoker type boiler that
burns a mixture of ground solid
waste and fuel oil to produce a low-
temperature, low-pressure steam.
The process then calls for the
steam to be superheated in a sepa-
rate facility for industrial
purposes.
COLLECTION AND TRANSPORTATION
Expenditures for collection and
transportation operations constitute
approximately 75 percent of the
estimated $4.5 billion spent each
year on solid waste management in
this country.
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The OSWMP is currently sup-
porting three projects involving
the movement of solid wastes via
hydraulic pipelines. A pneumatic
system used to collect waste from
high-rise apartments is success-
fully operating in Sweden. De-
signers of the Disney World facility
being built in Florida plan to
use a network of pipelines to
transport wastes to a central
location. It is expected that
pneumatic systems will be used at
several sites in the "Operation
Breakthrough" program of the U.S.
Department of Housing and Urban
Development.
The City of Wichita Falls,
Texas, uses a container-train and
"mother" truck method to collect
its municipal solid wastes. The
unique thing about the system, how-
ever, is that a computer is used to
optimize the collection operations.
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The city, with the support of an
OSWMP demonstration grant, has
equipped its collection vehicles
with devices that weigh the solid
waste as it is picked up. The
figures are electronically trans-
mitted to the computer, which
analyzes them by measuring them
against the location of the pick-up,
the characteristics of the particu-
lar neighborhood, and other
pertinent information. The computer
then schedules rendezvous points
for the "mother" truck and the
train to minimize waiting time,
which results in better utilization
of the city's equipment and person-
nel .
Compaction and shredding are
two other ways of processing solid
waste that are becoming increasingly
important in many solid waste man-
agement systems. Both can be used
to extend the life of a sanitary
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landfill. The OSWMP is currently
investigating the feasibility of
baling wastes and transporting
them from urban areas by rail.
Results to date suggest that such
a system has economic and technical
potential.
INCINERATION
New incineration methods have
been investigated recently. In
one project, a small-scale Torrax
system facility was built in 19&9
to dispose of 75 tons of municipal
solid waste daily. This project is
scheduled to be completed in June
1971o In the system, very hot air
is mixed with solid waste as it
passes into the top of a gasifier.
The primary purpose of the gasifier
is to decompose the organic and
hydrocarbon gases„ Only the non-
combustibles and difficult-to-burn
wastes reach the base of the
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gasifier. At that point, they are
either completely burned in the
high-temperature area or converted
to a molten slag, which becomes an
inert residue when immersed in
water. The combustible gases are
drawn into the igniter unit where
they are mixed with outside air and
completely burned. The exhaust from
the igniter is cooled in a water
spray tower or is used to generate
steam. The relatively cool exhaust
is cleansed of entrained particulate
matter as 'it passes through a
fabric dust collector and is then
discharged into the atmosphere.
Two incinerators that may be
used by smaller communities are
also being evaluated. One has a
rotating, saucer-shaped grate made
of perforated stainless-steel. Air
is. forced through the holes to
enhance the combustion of the
wastes. A 3,300 pound/hour
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incinerator demonstrated in
Shelbyville, Indiana, has a vortex
configuration. This enables it
to burn wastes faster than an
ordinary incinerator of the same
size because it has a higher heat-
release rate.
In a high-temperature incin-
eration process known as the
Melt-Zit, municipal solid waste
is charged midway up the stack.
The combustible materials burn
there, while the heavier non-
combustibles fall on the fuel bed
and are melted. The resulting
molten slag and iron flow from
the base of the unit, and, if
quenched rapidly in water, become
grit or sand-like particles, which
are sterile and inert.
Using a technique known as
pyrolysis (destructive distilla-
tion), the Bureau of Mines of the
U.S. Department of the Interior has
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proved that scrap tires can be
converted into useful byproducts.
The Firestone Tire and Rubber
Company, which supported this
research, is reportedly building
a ful1-scale uni t.
SOURCE REDUCTION
Perhaps one of the most chal-
lenging and perplexing questions
facing those concerned about the
increasing generation of solid
wastes is the matter of source
reduction. If products were re-
designed to serve the same function
they do now but created less waste
when discarded or could be more
easily recycled, we could, so to
speak, solve the problem before it
arose. For example, some progress
is being made in designing dis-
solvable or degradable bottles at
the University of Toronto in
Canada, the University of Aston in
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Birmingham, England, and Clemson
University in South Carolina. If
these materials can be perfected,
some of the problems associated
with containers will be solved.
THE FUTURE
These are examples of tech-
nologies that are emerging now.
What future methods will be
employed for solid waste management
is debatable. One thing is sure,
howevei—systems are becoming
more complex, place more emphasis
on resource recovery, and in many
cases are going to require a
regional approach to establish a
satisfactory system.
It should be stressed, however,
that total reliance must not be
placed on new technologies. There
is much that can be done now to
upgrade community solid waste
management practices. Responsible
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officials should replace antiquated
systems with available acceptable
methods, make improvements in
existing collection systems to
bring about greater efficiency and
economy of operation, and give
attention to putting their systems
on a sound management basis.
Only by this combination of
approaches can we be confident
that we are doing all that can be
done to conserve our Nation's
resource base.
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Mention of a aorrmeraial product does
not imply endorsement by the U.S.
Government.
* GPO : 1972 O - 462-459
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U.S. ENVIRONMENTAL PROTECTION AGENCY
1972
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